A leading cinema chain has equipped its employees with night vision goggles to prevent the latest Harry Potter film being illegally recorded.
Cinema manager Glenn Vosbergen demonstrates the goggles
Vue Cinemas - formerly Warner Village - has asked staff to check that audience members do not use video cameras to make pirate copies of the film.
Harry Potter and the Prisoner of Azkaban opened in the UK on Monday.
Hundreds of Potter fans turned out for Sunday night's premiere at the Odeon Leicester Square, in central London.
Jamie Graham, manager of the Vue complex in Ellesmere Port, Cheshire, said the monocle devices had been sent to outlets because of the extraordinary popularity of the film.
"I have been working in the cinema industry for 10 years and I have never heard of anything like this before," he said.
"Our ushers are using the goggles in every screening to check nobody is making any illegal recordings.
Daniel Radcliffe, Emma Watson and Rupert Grint arrive at the premiere
"If anybody is caught then they will be reported to the police."
Glenn Vosbergen, manager of the Vue cinema in Shepherd's Bush, London, demonstrated the goggles for BBC News Online and said they were a useful device for his staff.
"We have the goggles for a two-week trial period, mainly to prevent the Harry Potter film being copied and ending up on the net," he said.
"We've never caught anyone copying films here and we've had no problems as yet with Potter, but we are keeping a close eye on the audiences.
"These new goggles are extremely effective - they don't give off any light, so the customers can't see you using them."
Poor quality copies of the first two movies were freely available on the black market.
The goggles have been issued to Vue cinema staff
Using codes imprinted on the films as a security device, distributor Warner Brothers were able to trace some pirate DVD versions to Britain.
Three times as many fans watched the stars arrive at Sunday's screening as had turned out for the US premiere eight days earlier.
"It's bigger than New York and I didn't think that could be possible," said Harry Potter actor Daniel Radcliffe.
"I love it, it's just such fun," said Harry Potter author JK Rowling, who is estimated to have earned £435m from her creation.
Rowling was full of praise for Radcliffe and his young co-stars Emma Watson and Rupert Grint.
"You could not meet a nicer, saner bunch of people," she told reporters.